In the related art, a displacement sensor that detects the amount of displacement is widely used. This type of displacement sensor may be configured by using, for example, semiconductor (for example, JP 6-104380A (Reference 1), JP 8-213541A (Reference 2), and JP 2000-156464 (Reference 3)).
A semiconductor integrated circuit device described in Reference 1 includes a first semiconductor chip provided on a lower surface of an inner lead through a first insulating layer, and a second semiconductor chip provided on an upper surface of the inner lead through a second insulating layer. Each of the first semiconductor chip and the second semiconductor chip is provided with a bonding pad on each of the surfaces facing the same direction, and is wire-bonded to predetermined portions on the upper surface of the inner lead.
In a semiconductor device described in Reference 2, bump electrodes having the same function as each other in a first semiconductor chip and a second semiconductor chip are disposed to face each other and are connected to the same lead.
In a semiconductor device manufactured by a method for manufacturing a semiconductor device described in Reference 3, a first semiconductor chip and a second semiconductor chip are directed to surfaces (back surfaces) opposite to respective circuit formation surfaces (front surfaces) and are bonded to be fixed in a stacked state in which positions are shifted in a direction orthogonal to a disposition direction of external electrodes provided on the circuit formation surfaces.
For example, a vehicle, an airplane or the like may be provided with a plurality of circuits (for example, a detection unit) having the same function from the viewpoint of safety. In a case where such use is taken into account, in the technique described in Reference 1, wire bonding is performed by using an upper surface of an inner lead, and thereby, it is necessary to shift a position of each chip, and there is a possibility that sensing accuracies of each of the circuits are significantly different from each other in use in which a positional relationship between a sensing point such as a magnetic sensor and a detection target is important. In addition, in the technique described in Reference 2, a first semiconductor chip and a second semiconductor chip need to be disposed to interpose an inner lead therebetween, and thereby, more chips cannot be stacked, and thicknesses of components increase by thicknesses of bump electrodes which connect the inner lead, the first semiconductor chip, and the second semiconductor chip to each other. In addition, in the technique described in Reference 3, wire bonding is performed by using surfaces of a first semiconductor chip and a second semiconductor chip, which do not face each other, and thereby, thicknesses thereof increase by a height of a wire.
Thus, a need exists for a displacement sensor which is not susceptible to the drawback mentioned above.